The singer, 20, was pictured hobbling into Heathrow Airport yesterday after going under the knife in the US but is sure he'll be back on form by the time 1D go on tour in April.

'Hey guys I know most of you have seen those pics today! Yes I've had major knee surgery , a much larger surgery than first anticipated ,' TweetedNiall.

'But i would like to tell u , it was a complete success ! Considering the scale of it! So all I ask of you guys is that you would respect my privacy as I try to recover and get for the where we are tour!'

Niall had an op for torn ligaments in 2012 after
dislocating one of his joints playing football but revealed in April
that it'd been playing up during the group's Take Me Home tour.

Despite being back at home after his latest procedure, it seems Niall is still feeling a little peaky.

The blond star didn't think he was looking his best when he shared a cute Instagram photo with Directioners on Wednesday.

'Thank god for filters huh! Be in an awful state without them hahaha,' Niallcaptioned the snap.

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